1. Field of the Invention
The present invention relates to a bumper structure for an automobile formed by integrating a bumper reinforce and a bumper stay.
2. Description of the Related Art
In the inside of a bumper installed in the front end and rear end of a body of an automobile of a passenger car and truck and the like, a bumper reinforce is arranged as a reinforcing member. Generally, the bumper reinforce is a member of a hollow section including a front wall and rear wall facing generally perpendicularly to the loading direction and a plurality of lateral walls connecting the front wall and the rear wall, wherein both ends are supported by a pair of bumper stays and the rear end of respective stay is fixed to the front end of a (front or rear) side member.
Also, in the present specification, the collision face side is referred to as “front” and the vehicle body side is referred to as “rear”, regardless of the front side or rear side of the vehicle.
The bumper structure including such a bumper reinforce and bumper stays, wherein holes penetrating the front wall and rear wall in the vehicle longitudinal direction are formed in both end parts of the bumper reinforce, cylindrical shaft members of aluminum alloy are fit in to the holes, the shaft members are enlarged by electromagnetic forming to be tightly adhered to the inner peripheral surface of the holes and are extended toward the outer diameter direction between the front wall and rear wall, thereby the bumper reinforce and the shaft members (bumper stays) are fixed, is known by, for example, the Japanese Published Unexamined Patent Application No. 2004-237818, the Japanese Published Unexamined Patent Application No. 2007-284039, and the Japanese Published Unexamined Patent Application No. 2008-037220.